function safe_add(x, y) {
    var lsw = (x & 0xFFFF) + (y & 0xFFFF),
       msw = (x >> 16) + (y >> 16) + (lsw >> 16);
    return (msw << 16) | (lsw & 0xFFFF);
 }
 
 /*
 * Bitwise rotate a 32-bit number to the left.
 */
 function bit_rol(num, cnt) {
    return (num << cnt) | (num >>> (32 - cnt));
 }
 
 /*
 * These functions implement the four basic operations the algorithm uses.
 */
 function md5_cmn(q, a, b, x, s, t) {
    return safe_add(bit_rol(safe_add(safe_add(a, q), safe_add(x, t)), s), b);
 }
 function md5_ff(a, b, c, d, x, s, t) {
    return md5_cmn((b & c) | ((~b) & d), a, b, x, s, t);
 }
 function md5_gg(a, b, c, d, x, s, t) {
    return md5_cmn((b & d) | (c & (~d)), a, b, x, s, t);
 }
 function md5_hh(a, b, c, d, x, s, t) {
    return md5_cmn(b ^ c ^ d, a, b, x, s, t);
 }
 function md5_ii(a, b, c, d, x, s, t) {
    return md5_cmn(c ^ (b | (~d)), a, b, x, s, t);
 }
 
 /*
 * Calculate the MD5 of an array of little-endian words, and a bit length.
 */
 function binl_md5(x, len) {
    /* append padding */
    x[len >> 5] |= 0x80 << (len % 32);
    x[(((len + 64) >>> 9) << 4) + 14] = len;
 
    var i, olda, oldb, oldc, oldd,
       a = 1732584193,
       b = -271733879,
       c = -1732584194,
       d = 271733878;
 
    for (i = 0; i < x.length; i += 16) {
       olda = a;
       oldb = b;
       oldc = c;
       oldd = d;
 
       a = md5_ff(a, b, c, d, x[i], 7, -680876936);
       d = md5_ff(d, a, b, c, x[i + 1], 12, -389564586);
       c = md5_ff(c, d, a, b, x[i + 2], 17, 606105819);
       b = md5_ff(b, c, d, a, x[i + 3], 22, -1044525330);
       a = md5_ff(a, b, c, d, x[i + 4], 7, -176418897);
       d = md5_ff(d, a, b, c, x[i + 5], 12, 1200080426);
       c = md5_ff(c, d, a, b, x[i + 6], 17, -1473231341);
       b = md5_ff(b, c, d, a, x[i + 7], 22, -45705983);
       a = md5_ff(a, b, c, d, x[i + 8], 7, 1770035416);
       d = md5_ff(d, a, b, c, x[i + 9], 12, -1958414417);
       c = md5_ff(c, d, a, b, x[i + 10], 17, -42063);
       b = md5_ff(b, c, d, a, x[i + 11], 22, -1990404162);
       a = md5_ff(a, b, c, d, x[i + 12], 7, 1804603682);
       d = md5_ff(d, a, b, c, x[i + 13], 12, -40341101);
       c = md5_ff(c, d, a, b, x[i + 14], 17, -1502002290);
       b = md5_ff(b, c, d, a, x[i + 15], 22, 1236535329);
 
       a = md5_gg(a, b, c, d, x[i + 1], 5, -165796510);
       d = md5_gg(d, a, b, c, x[i + 6], 9, -1069501632);
       c = md5_gg(c, d, a, b, x[i + 11], 14, 643717713);
       b = md5_gg(b, c, d, a, x[i], 20, -373897302);
       a = md5_gg(a, b, c, d, x[i + 5], 5, -701558691);
       d = md5_gg(d, a, b, c, x[i + 10], 9, 38016083);
       c = md5_gg(c, d, a, b, x[i + 15], 14, -660478335);
       b = md5_gg(b, c, d, a, x[i + 4], 20, -405537848);
       a = md5_gg(a, b, c, d, x[i + 9], 5, 568446438);
       d = md5_gg(d, a, b, c, x[i + 14], 9, -1019803690);
       c = md5_gg(c, d, a, b, x[i + 3], 14, -187363961);
       b = md5_gg(b, c, d, a, x[i + 8], 20, 1163531501);
       a = md5_gg(a, b, c, d, x[i + 13], 5, -1444681467);
       d = md5_gg(d, a, b, c, x[i + 2], 9, -51403784);
       c = md5_gg(c, d, a, b, x[i + 7], 14, 1735328473);
       b = md5_gg(b, c, d, a, x[i + 12], 20, -1926607734);
 
       a = md5_hh(a, b, c, d, x[i + 5], 4, -378558);
       d = md5_hh(d, a, b, c, x[i + 8], 11, -2022574463);
       c = md5_hh(c, d, a, b, x[i + 11], 16, 1839030562);
       b = md5_hh(b, c, d, a, x[i + 14], 23, -35309556);
       a = md5_hh(a, b, c, d, x[i + 1], 4, -1530992060);
       d = md5_hh(d, a, b, c, x[i + 4], 11, 1272893353);
       c = md5_hh(c, d, a, b, x[i + 7], 16, -155497632);
       b = md5_hh(b, c, d, a, x[i + 10], 23, -1094730640);
       a = md5_hh(a, b, c, d, x[i + 13], 4, 681279174);
       d = md5_hh(d, a, b, c, x[i], 11, -358537222);
       c = md5_hh(c, d, a, b, x[i + 3], 16, -722521979);
       b = md5_hh(b, c, d, a, x[i + 6], 23, 76029189);
       a = md5_hh(a, b, c, d, x[i + 9], 4, -640364487);
       d = md5_hh(d, a, b, c, x[i + 12], 11, -421815835);
       c = md5_hh(c, d, a, b, x[i + 15], 16, 530742520);
       b = md5_hh(b, c, d, a, x[i + 2], 23, -995338651);
 
       a = md5_ii(a, b, c, d, x[i], 6, -198630844);
       d = md5_ii(d, a, b, c, x[i + 7], 10, 1126891415);
       c = md5_ii(c, d, a, b, x[i + 14], 15, -1416354905);
       b = md5_ii(b, c, d, a, x[i + 5], 21, -57434055);
       a = md5_ii(a, b, c, d, x[i + 12], 6, 1700485571);
       d = md5_ii(d, a, b, c, x[i + 3], 10, -1894986606);
       c = md5_ii(c, d, a, b, x[i + 10], 15, -1051523);
       b = md5_ii(b, c, d, a, x[i + 1], 21, -2054922799);
       a = md5_ii(a, b, c, d, x[i + 8], 6, 1873313359);
       d = md5_ii(d, a, b, c, x[i + 15], 10, -30611744);
       c = md5_ii(c, d, a, b, x[i + 6], 15, -1560198380);
       b = md5_ii(b, c, d, a, x[i + 13], 21, 1309151649);
       a = md5_ii(a, b, c, d, x[i + 4], 6, -145523070);
       d = md5_ii(d, a, b, c, x[i + 11], 10, -1120210379);
       c = md5_ii(c, d, a, b, x[i + 2], 15, 718787259);
       b = md5_ii(b, c, d, a, x[i + 9], 21, -343485551);
 
       a = safe_add(a, olda);
       b = safe_add(b, oldb);
       c = safe_add(c, oldc);
       d = safe_add(d, oldd);
    }
    return [a, b, c, d];
 }
 
 /*
 * Convert an array of little-endian words to a string
 */
 function binl2rstr(input) {
    var i,
       output = '';
    for (i = 0; i < input.length * 32; i += 8) {
       output += String.fromCharCode((input[i >> 5] >>> (i % 32)) & 0xFF);
    }
    return output;
 }
 
 /*
 * Convert a raw string to an array of little-endian words
 * Characters >255 have their high-byte silently ignored.
 */
 function rstr2binl(input) {
    var i,
       output = [];
    output[(input.length >> 2) - 1] = undefined;
    for (i = 0; i < output.length; i += 1) {
       output[i] = 0;
    }
    for (i = 0; i < input.length * 8; i += 8) {
       output[i >> 5] |= (input.charCodeAt(i / 8) & 0xFF) << (i % 32);
    }
    return output;
 }
 
 /*
 * Calculate the MD5 of a raw string
 */
 function rstr_md5(s) {
    return binl2rstr(binl_md5(rstr2binl(s), s.length * 8));
 }
 
 /*
 * Calculate the HMAC-MD5, of a key and some data (raw strings)
 */
 function rstr_hmac_md5(key, data) {
    var i,
       bkey = rstr2binl(key),
       ipad = [],
       opad = [],
       hash;
    ipad[15] = opad[15] = undefined;
    if (bkey.length > 16) {
       bkey = binl_md5(bkey, key.length * 8);
    }
    for (i = 0; i < 16; i += 1) {
       ipad[i] = bkey[i] ^ 0x36363636;
       opad[i] = bkey[i] ^ 0x5C5C5C5C;
    }
    hash = binl_md5(ipad.concat(rstr2binl(data)), 512 + data.length * 8);
    return binl2rstr(binl_md5(opad.concat(hash), 512 + 128));
 }
 
 /*
 * Convert a raw string to a hex string
 */
 function rstr2hex(input) {
    var hex_tab = '0123456789abcdef',
       output = '',
       x,
       i;
    for (i = 0; i < input.length; i += 1) {
       x = input.charCodeAt(i);
       output += hex_tab.charAt((x >>> 4) & 0x0F) +
          hex_tab.charAt(x & 0x0F);
    }
    return output;
 }
 
 /*
 * Encode a string as utf-8
 */
 function str2rstr_utf8(input) {
    return unescape(encodeURIComponent(input));
 }
 
 /*
 * Take string arguments and return either raw or hex encoded strings
 */
 function raw_md5(s) {
    return rstr_md5(str2rstr_utf8(s));
 }
 function hex_md5(s) {
    return rstr2hex(raw_md5(s));
 }
 function raw_hmac_md5(k, d) {
    return rstr_hmac_md5(str2rstr_utf8(k), str2rstr_utf8(d));
 }
 function hex_hmac_md5(k, d) {
    return rstr2hex(raw_hmac_md5(k, d));
 }
 
 /** 
  * 暴露接口给小程序 因为export default，所以引入的时候可以自定义方法名称 
  * +--------------------
  * @param {String}   string  需要加密的字符串
  * @param {String}   key     加密key
  * @param {Boolean}  raw     规则 false: 返回hex_md5, true: 返回raw_md5
  */
 export default function md5(string, key, raw) {
    if (!key) {
       if (!raw) {
          return hex_md5(string);
       }
       return raw_md5(string);
    }
    if (!raw) {
       return hex_hmac_md5(key, string);
    }
    return raw_hmac_md5(key, string);
 }